Neuromodulation of the Left Inferior Frontal Cortex Affects Social Monitoring during Motor Interactions

Area of Science:

• Neuroscience
• Cognitive Science
• Social Cognition

Background:

• Social monitoring is crucial for motor interactions.
• The ventral premotor cortex (vPMc) is implicated in action observation and motor planning.
• Previous fMRI studies suggested left vPMc involvement in social monitoring, but its causal role remained unclear.

Purpose of the Study:

• To investigate the causal role of the left vPMc in social monitoring during interactive motor tasks.
• To test if neuromodulation of the left vPMc affects performance when a partner's actions violate expectations.

Main Methods:

• Three experiments used transcranial direct current stimulation (tDCS) over the left lateral frontal cortex during a turn-based musical interaction task.
• Participants performed a music-like task with a virtual partner who unexpectedly deviated from expected actions in 50% of trials.
• Anodal, cathodal, and sham tDCS were applied to modulate left vPMc activity.

Main Results:

• Unexpected partner actions led to performance slowdowns (observation-induced posterror slowing) during sham stimulation.
• Cathodal tDCS reduced this slowdown, while anodal tDCS enhanced it, indicating opposing modulatory effects.
• Neuromodulation effects were specific to interactive contexts and unexpected partner behaviors.

Conclusions:

• The findings provide causal evidence for the left vPMc's role in social monitoring during motor interactions.
• The left vPMc may mediate the detection and processing of unexpected actions in social contexts.
• This region likely interacts with other brain areas, such as the posterior medial frontal cortex, to facilitate social monitoring.